The present invention relates to a safety device for the building field, for individually protecting against falls workers assigned to walking at high elevations in buildings under construction.
Safety devices for buildings are known for providing individual protection against falls of workers assigned to walking at high elevations in buildings under construction.
These devices generally comprise a plurality of metal poles, which are mutually spaced and are connected, at their base, to a horizontal surface of the building, constituted for example by a beam, and have, at their top end or in an intermediate region of their vertical extension, a passage for a cable, which is fixed to the building at its ends and is tensioned by means of suitable cable tensioning elements so as to form a safety parapet.
In these devices, the poles are merely meant to keep the cable at a preset height, so that it is easily engaged by the spring-clips of the safety belts or harnesses worn by workers.
U.S. Ser. No. 09/645,560 by the same Applicants, which is herein included by reference, illustrates a safety device significantly reducing the stresses transmitted from the cable to the pole transversely to the axis of the pole and allows to distribute over multiple poles the stresses transmitted along the cable, thus reducing the stresses discharged onto each pole.
Although this device ensures a better performance than conventional safety devices, it has limitations of application when the spacing between the poles becomes considerable. This device in fact offers adequate assurances of safety, with acceptable dimensions of the pole and of the system for connection to the surface of the building, for pole spacings up to approximately 10 m. When greater spacings are required, in order to work safely it would be necessary to oversize considerably the pole and the insert embedded in the concrete component to which the pole is rigidly coupled. This would inevitably entail an increase in the weight of the device and in its cost. Furthermore, with this device it is technically inadvisable to have pole spacings of more than 10 m, since beyond this limit in operating conditions the forces that become involved are different not only in terms of load but also in terms of multiple traction components: the pole might tip not only in the direction of the cable but also at right angles, since the cable would oscillate laterally. So-called xe2x80x9cwhiplashxe2x80x9d, i.e., dynamic stresses that are highly amplified and are composed of forces that are parallel and perpendicular to the line of the cable, causing tipping or oscillations of the poles, might also occur.
Another limit that can be observed in known types of device is the fact that these devices have been conceived mainly to be installed on prefabricated beams, i.e., on components that have a reduced transverse dimension. Because of this, the accidental fall of the worker is very close to the ideal tension line of the cable and therefore produces on the cable a force that has a modest lateral component, which can be withstood easily both by means of the cable and by means of the base for interlocking and resting the pole in and on the beam.
If these safety devices were installed on wider structural elements, such as for example prefabricated concrete floor or covering slabs, the traction components directed laterally to the cable would increase considerably, since any fall of the worker would be laterally quite distant from the ideal tension line of the cable. The cable, by touching the lateral edge of the concrete component, would in fact generate an additional significant lever arm and would introduce a torque and/or flexural moment that are difficult to re-center on the pole.
Moreover, it should be noted that prefabricated slabs (which are usually 10-20 meters long but are sometimes as long as 30 m) are often transported when they are already pre-impermeabilized with bitumen coats, except for the ends where the inserts for facilitating their lifting are inserted.
In such cases it is unfeasible to maintain a limited spacing between the poles, since it would be necessary to pierce the coat at the insert in order to connect the base of the poles.
Particularly for these kinds of components, there is a need to have a safety device for individually protecting against falls workers assigned to walking at high elevations in buildings under construction, which offers adequate assurances of safety even with considerable pole spacings.
The aim of the present invention is indeed to provide a safety device for the building field, for individually protecting against falls workers assigned to walking at high elevations in buildings under construction which is capable of withstanding forces, even considerable ones, orientated transversely to the line of the cable in the presence of large pole spacings.
Within this aim, an object of the invention is to provide a device that can adapt itself without problems to different operating conditions and to different types of prefabricated component.
Another object of the invention is to provide a device that is simple to use and offers the greatest assurances of safety.
This aim and these and other objects that will become better apparent hereinafter are achieved by a safety device for the building field, for individually protecting against falls workers assigned to walking at high elevations in buildings under construction, which comprises at least one pole and means for detachably connecting the base of said pole to the surface of a building; said pole having, proximate to its top end, engagement means for a cable element that is suitable to form a safety parapet, characterized in that it comprises at least one leg which is connected laterally to said pole and can rest, with its lower end, on said surface of the building, laterally to the region engaged by the base of said pole, in order to form, for said pole, an auxiliary resting element for pushing against said surface of the building.